It's walking in place, so you don't need a treadmill. In fact, a treadmill wouldn't work, because sometimes she has you doing side steps or forward-and-back movements.
ETA: I assume you're talking about the Leslie Sansone videos? If you mean some other walking video then I don't know the answer.
These videos are so good to begin with. I started with the 1 mile walk and worked my way up to walking up hills in my neighborhood. I eventually moved onto to a tougher video (Slim in Six) and lost 30 pounds (too bad I gained it back!!!!) But if you're just starting out these tapes/dvd's are good for building up your endurance. Good Luck!
Yes, they are. I have several of them, and they're all good. As a rule, I prefer dancier routines or step aerobics, but for the days when I want something that isn't that complicated, the Leslie Sansone videos are perfect.